1. Field of the Invention
The present invention relates to a high frequency module used for electronic apparatuses and electronic devices including portable information terminals, wireless LANs, WLLs (Wireless Local Loop). In particular, this invention relates to a small size, high performance, low cost high-frequency module with a unitary structure incorporating a high frequency amplification device together with a high frequency filter or a high frequency splitter.
2. Description of the Related Art
A high frequency module generally includes inside a high frequency power amplifier device, and a high frequency filter or a high frequency splitter disposed in the vicinity of the power amplifier device.
With the recent increase in transmission capacity and transmission speed in mobile communication systems, the quantities of heat radiated by the high frequency power amplifier devices have been increasing to deal with the great deal of high frequency energy.
However, such high frequency filters and high frequency splitters are susceptive to heat. Specifically, surface acoustic wave filter used for the high frequency filter or the high frequency splitter is a device generally including a piezoelectric substrate made of lithium tantalite or the like formed with a comb-shaped electrode for propagating surface acoustic waves. Since the electric properties of the piezoelectric substrate itself are greatly influenced by temperature changes, it needs to be disposed apart from the heating element such as the high frequency power amplifier device provided inside the module. In addition, this problem is not only with SAW (Surface Acoustic Wave) devices but also with FBARs (Film Bulk Acoustic Resonator) and BAWs (Bulk Acoustic Wave Filter). These thermally unstable devices are hereinafter collectively referred to as “filter component”.
For this reason, conventional high frequency modules with a unitary structure incorporating the high frequency power amplifier device, the high frequency filter or the like are unable to sufficiently meet the recent demand for miniaturization, lightening, high density packaging, and cost reduction of mobile communication terminals and the like.